Sensor jacket

ABSTRACT

A sensor guide wire includes a sensor element arranged in a jacket in a sensor region of the sensor guide wire; a core wire extending at least partly along a length of the sensor guide wire; and at least one electrical lead connected to the sensor element. The jacket is tubular and includes proximal and distal end openings, a jacket wall, a first opening arranged in the jacket wall, and a second opening arranged in the jacket wall, the first and second openings being proximate to the sensor element. The core wire is adapted to extend through the jacket via the proximal and distal end openings. At least a portion of the first opening and at least a portion of the second opening are both located in the same cross-section of the sensor guide wire, the cross-section being perpendicular to the longitudinal axis of the sensor guide wire.

FIELD OF THE INVENTION

The present invention relates generally to sensor and guide wireassemblies, in which a sensor element is mounted at the distal end of aguide wire for intravascular measurements of physiological variables ina living body, and particularly to the mounting arrangement of thesensor element, and more particularly to a jacket in which the sensorelement is disposed, according to the preamble of the independent claim.

BACKGROUND OF THE INVENTION

In many medical procedures, various physiological conditions presentwithin a body cavity need to be monitored. These physiologicalconditions are typically physical in nature—such as pressure,temperature, rate-of-fluid flow, and provide the physician or medicaltechnician with critical information as to the status of a patient'scondition.

One device that is widely used to monitor conditions is the bloodpressure sensor. A blood pressure sensor senses the magnitude of apatient's blood pressure, and converts it into a representativeelectrical signal that is transmitted to the exterior of the patient.

For most applications it is required that the sensor is electricallyenergized. Some means of signal and energy transmission is thusrequired, and most commonly extremely thin electrical cables, sometimescalled microcables, are provided inside a guide wire, which itself isprovided in the form of a tube, which often has an outer diameter in theorder of 0.35 mm, and oftentimes is made of steel.

In order to increase the bending strength of the tubular guide wire, acore wire is positioned inside the tube. The core wire also helps toimprove “pushability” and “torquability” of the guide wire. Thementioned electrical cables are e.g. positioned in the space between theinner lumen wall and the core wire.

Sensor and guide wire assemblies in which a sensor is mounted at thedistal end of a guide wire are known. In U.S. Pat. No. Re. 35,648, whichis assigned to the present assignee, an example of such a sensor andguide wire assembly is disclosed, where a sensor guide comprises asensor element, an electronic unit, a signal transmitting cableconnecting the sensor element to the electronic unit, a flexible tubehaving the cable and the sensor element disposed therein, a solid metalwire, and a coil attached to the distal end of the solid wire. Thesensor element comprises a pressure sensitive device, typically amembrane, with piezoresistive elements connected in a Wheatstonebridge-type of arrangement mounted thereon.

As is disclosed in, for example, U.S. Pat. No. 6,167,763, which also isassigned to the present assignee, the sensor element can be arrangedinside a short tube (usually referred to as a sleeve or jacket), whichprotects the sensor element and comprises an aperture through which thepressure sensitive device is in contact with the ambient medium. TheU.S. Pat. No. 6,167,763 further illustrates that a first coil may beattached to the distal end of the jacket and that a similar second coilmay be attached to the proximal end of the jacket. The solid metalwire—which, as also mentioned above, in the art usually is referred toas the core wire—extends through the interior of the jacket and may beprovided with an enlarged diameter portion adapted for mounting of thesensor element.

U.S. Pat. No. 7,222,539 discloses a jacket, wherein a sensor element anda core wire are provided in separate compartments. Another example of asensor guide wire comprising a sensor enclosed by a sensor housing isdisclosed in WO 2006/037082 A2.

In WO 03094693 A2, a pressure-measuring apparatus is disclosed, thepressure-measuring apparatus comprises a sensor transducer adapted to beincorporated in a catheter.

DE 2420610 A1, discloses a sensor for measuring pressure, the sensor isadapted to be incorporated in a catheter. The sensor is enclosed by aprotecting tube.

U.S. Pat. No. 6,019,728 discloses a catheter including a catheter tubeto be inserted into a body. A plurality of sensing portions are arrangedin the catheter tube. Two pressure communication holes are provided inthe wall of the catheter tube to communicate the ambient pressure of thetube into the interior of the tube.

In US 2007088220 A1 an implantable medical device including aphysiological sensor is disclosed. The sensor is embedded in a meshstructure of a stent-like structure.

In US 20050187487 A1 and US 20060211946 A1, further examples ofcatheters provided with sensors are disclosed.

U.S. Pat. No. 6,162,182 discloses a cannula usable to remove blood froma patient during surgery.

Generally, a sensor and guide wire assembly comprises a sensor elementin the form of an elongated, essentially rectangular chip with apressure sensitive member in the form of a membrane provided thereon.The sensor chip is arranged inside a jacket, which besides the sensorchip also accommodates a portion of a core wire and at least oneelectrical lead connected to the sensor element. A first coil may beattached to the distal end of the jacket, and optionally a second coilmay be attached to the proximal end of the jacket. The first and secondcoils may be attached to the respective end of the jacket, e.g. bygluing, or alternatively soldering.

Although sensor and guide wire assemblies comprising a jacket designedaccording to the techniques presented by the present assignee inpractise have proven to work very well, there are continuously ongoingefforts to improve the performance and functionality of the sensor andguide wire assemblies.

According to the prior art, the jacket is provided with an aperture orwindow, through which the pressure sensitive part (typically a membrane)of the sensor element is in communication with a surrounding medium,e.g. blood. Now, it has—for the first time—been recognized that thedimensions of the aperture, the sensor element and the interior of thejacket in combination with the particular mounting arrangement of thesensor element are such that air present within the jacket and/oradhering to the surface of the jacket or sensor element has a tendencyto be entrapped within the jacket and/or forming an air bubble coveringthe aperture in the jacket. In other words, the ambient fluid (e.g.blood) does not wet the sensor element and the membrane completely,which affects the signal quality of the device.

An object of the present invention is therefore to provide a sensor andguide wire assembly comprising an improved jacket, with which theabove-mentioned wetting problem is eliminated or at least minimized.

SUMMARY OF THE INVENTION

By providing a jacket with multiple holes an improved wetting can beachieved, which ensures a more reliable and stable sensor output.

The sensor guide wire for intravascular measurements of at least onephysiological, or other, variable in a living body, in accordance withthe present invention, comprises a sensor element arranged in a jacketin a sensor region of said sensor guide wire, a core wire extending atleast partly along the length of said sensor guide wire, at least oneelectrical lead connected to said sensor element, wherein said jacket istubular and provided with a jacket wall, and further comprises a firstopening arranged in said jacket wall, said jacket is further providedwith proximal and distal end openings, and wherein a core wire isadapted to extend through said jacket via said proximal and distal endopenings, and wherein the sensor guide wire has an outer diameter ofapproximately 0.35 mm, and wherein said jacket further comprises atleast a second opening arranged in said jacket wall.

SHORT DESCRIPTION OF THE APPENDED DRAWINGS

FIG. 1 illustrates schematically the general design of a sensor andguide wire assembly according to the prior art.

FIG. 2 shows a portion of the sensor and guide wire assembly of FIG. 1,and illustrates how air can be entrapped within a jacket and form abubble on the surface of a jacket according to the prior art.

FIG. 3 illustrates a jacket according to a first embodiment of thepresent invention.

FIG. 4a illustrates a sensor guide wire and a jacket according to asecond embodiment of the present invention.

FIG. 4b illustrates the jacket according to the second embodiment, alsoshown in FIG. 4a , of the present invention.

FIG. 5 shows a jacket according to a third embodiment of the presentinvention.

FIG. 6 shows a jacket according to a fourth embodiment of the presentinvention.

FIG. 7a shows a sensor guide wire and a jacket according to a fifthembodiment of the present invention.

FIG. 7b illustrates the jacket from above according to the fifthembodiment, also shown in FIG. 7a , of the present invention.

FIG. 8 shows a jacket according to a sixth embodiment of the presentinvention.

FIG. 9 shows a jacket according to a seventh embodiment of the presentinvention.

FIG. 10 is a schematic view of a jacket that includes openings that arewider in their distal parts than in their proximal parts.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

For better understanding of the context in which the present inventionis going to be used, a sensor and guide wire assembly 1 of aconventional design is illustrated in FIG. 1. The sensor guide 1comprises a hollow tube 2, a core wire 3, a first coil 4, a second coil5, a jacket or sleeve 6, a dome-shaped tip 7, a sensor element or chip8, and one or several electrical leads 9. The proximal end of the firstcoil 4 is attached to the distal end of the hollow tube 2, while thedistal end of the first coil 4 is attached to the proximal end of thejacket 6. The proximal end of the second coil 5 is connected to thedistal end of the jacket 6, and the dome-shaped tip 7 is attached to thedistal end of the second coil 5. The core wire 3 is at least partlydisposed inside the hollow tube 2 such that the distal portion of thecore wire 3 extends out of the hollow tube 2 and into the second coil 5.The sensor element 8 is mounted on the core wire 3 at the position ofthe jacket 6, and is through the electrical leads 9 connected to anelectronic unit (not shown in FIG. 1). The sensor element 8 comprises apressure sensitive device in the form of a membrane 10, which through anaperture 11 in the jacket 6 is in communication with a medium, such asblood, surrounding at least the distal portion of the sensor guide 1. Atthe proximal end of the sensor guide 1 each electrical lead is connectedto a conductive member 12 and the conductive members 12 are insulatedfrom each other by insulating members 13, to thereby form a maleconnector for the sensor guide 1.

Although not shown in FIG. 1, the sensor element 8 further comprises anelectrical circuitry, which in a Wheatstone bridge-type of arrangementis connected to one or several piezoresistive elements provided on themembrane 10. As is well known in the art, a certain pressure exerted onthe membrane 10 from the surrounding medium will thereby correspond to acertain stretching of the membrane 10 and thereby to a certainresistance of the piezoresistive elements mounted thereon and, in turn,to a certain output from the sensor element 8.

FIG. 2 shows the jacket portion of the sensor guide 1 of FIG. 1, andillustrates how air 14 can be entrapped within the jacket 6 or form abubble 15 covering the aperture 11 in the jacket 6. Clearly, the airbubble 15, which covers the aperture 11, will create some undefinedintermediate medium which prevents direct fluid contact between theambient medium (typically blood) and the pressure sensitive membrane 10,and it should also be clear that if the air bubble 15, or parts thereof,disappears, the output from sensor element 8 will be affected. Air 14entrapped within the jacket 6 exerts pressure on the sensor element 8and can induce stress in the membrane or in the sensor element 8, whoseoutput can change if the air 14 escapes out of the jacket 6 during useof the sensor guide 1. The above explanations of how air can affect themeasurements are merely intended to be suggestive, but it should beclear that all uncontrolled factors should be eliminated in order toproduce a sensor and guide wire which is as reliable as possible. Here,it can be mentioned that the standard outer diameter of a sensor guideis only 0.35 mm (0.014 inch), while an aperture in a jacket can have adiameter of about 0.25 mm.

To solve the problems outlined above, the present inventors suggest asensor and guide wire comprising a jacket 20 with multiple openings,which allows for complete or at least improved wetting of the sensorelement 18 and membrane. In contrast to the previously known jackets,which have only a first opening, through which first opening a membranesenses e.g. the surrounding pressure, and end openings, through which acore wire extends, the jacket 20 comprises further at least a secondopening 23.

In FIG. 3 a first embodiment of a jacket 20 for a sensor and guide wireassembly, for intravascular measurements of at least one physiological,or other, variable in a living body, is schematically illustrated. Thejacket 20 is tubular and provided with a jacket wall 21, and comprises afirst opening 22 arranged in said jacket wall 21. Through this firstopening 22, or at least through the first opening 22, the sensor element18 (not shown in FIG. 3) is adapted to sense one or many physiological,or other, variables. The jacket 20 further comprises at least a secondopening 23 arranged in the jacket wall 21. The second opening 23 allowsthe entrapped air within the jacket 20 to escape out from the jacket 20,or even prevents entrapped air to occur. A second opening 23 alsoprovides for a better fluid communication, which prevents an air bubblefrom being formed over the aforementioned aperture in the jacket 20.According to this preferred embodiment the second opening 23 is arrangedat the opposite side of the tubular jacket 20 in relation to said firstopening 22. Further, the jacket 20 is hollow and may be provided withproximal and distal end openings (29, 30).

According to a preferred embodiment of the present invention, and asalso shown in FIG. 3, the jacket 20 has a longitudinal axis 31, and thejacket wall 21 extends essentially parallel to said longitudinal axis31. The jacket 20 may have a circular, a square, or an oval crosssection in a plane perpendicular to said longitudinal axis 31.

In FIG. 4a , a sensor guide wire 24 and a jacket 20 according to asecond embodiment of the present invention, is shown. The sensor guidewire 24 comprises a hollow tube 25, a core wire 26, at least a secondcoil 27, a sensor element 18 arranged in a jacket 20 in a sensor regionof said sensor guide wire 24, a dome-shaped tip 28, and one or severalelectrical leads (not shown). As is shown in FIG. 4a , the jacket 20 isfixed relative to the core wire 26. In this embodiment, the jacket 20 isprovided with a plurality of elongated openings 22, 23, 33, 34, 35, 36,37 (23, 34, 37 not shown in FIG. 4a ) distributed at the jacket wall 21all around the jacket 20, which allows air entrapped within the jacket20 to escape out therefrom.

FIG. 4b also illustrates the jacket 20 according to the secondembodiment of the present invention. The jacket 20 has a first opening22 and a second opening 23 arranged at the opposite side of the jacket20 in relation to the first opening 22. In addition, the jacket 20 isprovided with yet further five openings denoted 33, 34, 35, 36 and 37.Thus, according to the second embodiment of the present invention thejacket 20 is provided with seven openings 22, 23, 33, 34, 35, 36, 37distributed at the jacket wall 21 all around the jacket 20, which areconfigured to allow a pressure sensitive device of the sensor element 18to be in communication with a medium surrounding the jacket 20.

As shown in FIGS. 4a and 4b , the openings 33, 34, 35 (in this case,three openings) constitute a first set of a plurality of openings. Atleast a portion of the openings 33, 34, 35 in the first set are locatedin a same first cross-section A-A (shown in FIG. 4b ) of the sensorguide wire, the first cross-section A-A being perpendicular to alongitudinal axis of the sensor guide wire 24. As also shown in FIGS. 4aand 4b , the openings 22, 36, 37 (in this case, three openings)constitute a second set of a plurality of openings. At least a portionof the openings 22, 36, 37 in the second set are located in a samesecond cross-section B-B (shown in FIG. 4b ), the second cross-sectionB-B being perpendicular to a longitudinal axis of the sensor guide wire24. The first set of openings 33, 34, 35 extending through the jacketwall includes a first opening 33 located above the sensor element, asecond opening 34 located at a first lateral side of the sensor element,and a third opening 35 located at a second lateral side of the sensorelement. The first, second, and third openings 33, 34, 35 are elongatedin a longitudinal direction of the jacket 20, and are aligned in acircumferential direction of the jacket 20. The second set of openings22, 36, 37 include a fourth opening 22 that is aligned with the firstopening 33 in a longitudinal direction of the jacket 20, a fifth opening37 that is aligned with the second opening 34 in the longitudinaldirection of the jacket, and a sixth opening 36 that is aligned with thethird opening 35 in the longitudinal direction of the jacket. Thefourth, fifth, and sixth openings 22, 36, 37 are elongated in thelongitudinal direction of the jacket 20. The jacket also includes aseventh opening, which is the opening 23.

In FIG. 5 the jacket 20 according to a third embodiment of the presentinvention, is illustrated. The jacket 20 has exactly three openings thatare aligned in the circumferential direction of the jacket 20: a firstopening 22, a second opening 23 and a third opening 33. As shown in FIG.5, first opening 22 is to be located above the sensor element, thesecond opening 23 is to be located at a first lateral side of the sensorelement, and the third opening 33 is to be located at a second lateralside of the sensor element. The jacket 20 has a circular cross sectionin a plane perpendicular to the longitudinal axis 31 and the openings22, 23, 33 are arranged evenly distributed around said jacket wall 21.

FIG. 6 shows the jacket 20 according to a fourth embodiment of to thepresent invention. According to this embodiment, the jacket 20 has afirst 22 and a second 23 opening and is further provided with proximaland distal end openings 29, 30. Furthermore, the jacket 20 is providedwith yet further a plurality of elongated openings 33, 34, 35, 36, theopenings 33, 34, 35, 36 having different sizes in relation to eachother.

FIG. 7a shows the sensor guide wire 24 and the jacket 20 according to afifth preferred embodiment of the present invention. The jacket 20 isprovided with proximal and distal end openings 29, 30 and a core wire 26extends through said jacket 20 via the proximal and distal end openings29, 30. Further, the jacket 20 is provided with a first 22, a second 23,a third 33, and a fourth opening 34, which openings are arranged inpairs on opposite sides of the jacket 20. According to this preferredembodiment, the openings 22, 23, 33, 34 are asymmetrical. The first andthe fourth openings 22, 34 (not shown in FIG. 7a ), arranged on a firstside 38 of the jacket 20, are wider in a distal part than in a proximalpart of the openings 22, 34. Whereas the second and the third openings23, 33, arranged on a second side 39, opposite to the first side 38 ofthe jacket 20, are wider in a proximal part than in a distal part of theopenings 23, 33. In other words, as shown in FIG. 7b , distal edges 22b, 34 b of the openings 22, 34, which extend in a substantiallycircumferential direction around the jacket 20, are longer than proximaledges 22 a, 34 a of the openings 22, 34, which also extend in asubstantially circumferential direction around the jacket 20. And, asalso shown in FIG. 7b , proximal edges 23 a, 33 a of the openings 23,33, which extend in a substantially circumferential direction around thejacket 20, are longer than distal edges 23 b, 33 b of the openings 23,33, which also extend in a substantially circumferential direction aboutthe jacket 20. The openings 22, 23, 33, 34 are configured to allow apressure sensitive device of the sensor element 18 to be incommunication with a medium surrounding the jacket 20. An advantage ofthe openings of the two pairs being wider in different parts (distallyor proximally) at different sides, is that it is not possible to arrangethe jacket 20 in an incorrect direction when assembling the jacket 20and the sensor guide wire 24. Thus, the openings at for example thefirst side 38 will be arranged in the same way independent of which oneof the end openings 29, 30 of the jacket 20 is being arranged e.g.distally. Another advantage of this embodiment is that, the fluid usedfor flushing the sensor guide wire comprising the jacket 20 beforeinsertion of the sensor guide wire, in greater extent stays inside thejacket 20 when flushed right through the jacket 20.

FIG. 7b illustrates the jacket 20 from above according to the fifthembodiment of the present invention. FIG. 7b illustrates that the twopairs of openings 22, 23, 33, 34 are arranged on opposite sides 38, 39of the jacket 20.

According to another embodiment of the present invention, the openings22, 23, 33, 34 arranged in pairs on opposite sides of the jacket 20 maybe slightly displaced in relation to each other along the longitudinalaxis 31.

In FIG. 8 the jacket 20 according to a sixth embodiment of the presentinvention, is illustrated. According to this embodiment, the jacket wall21 is mesh-like, and thus provided with a plurality of openings evenlydistributed at said jacket wall 21. In other words, in this embodiment,the jacket 20 is a mesh jacket 20 having a jacket wall 21 with aplurality of evenly distributed openings of substantially the same sizeand shape, as is shown in FIG. 8. The evenly distributed openings areconfigured to allow a pressure sensitive device of the sensor element 18to be in communication with a medium surrounding the jacket 20.

FIG. 9 shows the jacket 20 according to a seventh embodiment of thepresent invention. In this embodiment the jacket wall 21 is mesh-like,and further the jacket 20 is provided with a first 22 and a secondopening 23. The second opening 23 is arranged at the opposite side ofthe tubular jacket 20 in relation to said first opening 22. The jacket20 is hollow and may be provided with proximal and distal end openings29, 30. In other words, the jacket 20 is a mesh jacket 20 having ajacket wall 21 with a plurality of evenly distributed openings ofsubstantially the same size and shape, and further including a firstopening 22 and a second opening 23, wherein the first and secondopenings 22, 23 are larger than the evenly distributed openings in thejacket wall 21, as is shown in FIG. 9. The evenly distributed openingsand the first and second openings 22, 23 are configured to allow apressure sensitive device of the sensor element 18 to be incommunication with a medium surrounding the jacket 20.

It should be noted that previous embodiments are applicable, regardingthe number of openings and how they are arranged, in a jacket providedwith a mesh-like wall.

The present invention is not limited to the above-described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention, which is defined by the appending claims.

The invention claimed is:
 1. A sensor guide wire for intravascularmeasurement of a physiological variable, comprising: a core wireextending at least partly along a length of the sensor guide wire; asensor element mounted on the core wire, in a sensor region of thesensor guide wire, the sensor element comprising a pressure sensitivedevice; a jacket having a jacket wall, the jacket being fixed relativeto the core wire; and at least one lead connected to the sensor element;wherein the jacket is tubular and includes a proximal end opening, adistal end opening, and a first set of openings extending through thejacket wall, wherein the core wire extends through the jacket via theproximal and distal end openings, and wherein the first set of openingsextending through the jacket wall includes a first opening located abovethe sensor element, a second opening located at a first lateral side ofthe sensor element, and a third opening located at a second lateral sideof the sensor element, and wherein the first, second, and third openingsare elongated in a longitudinal direction of the jacket, and are alignedin a circumferential direction of the jacket.
 2. The sensor guide wireaccording to claim 1, wherein the jacket further includes a second setof openings extending through the jacket wall, the second set ofopenings including a fourth opening that is aligned with the firstopening in a longitudinal direction of the jacket, a fifth opening thatis aligned with the second opening in the longitudinal direction of thejacket, and a sixth opening that is aligned with the third opening inthe longitudinal direction of the jacket, wherein the fourth, fifth, andsixth openings are elongated in the longitudinal direction of thejacket.
 3. The sensor guide wire according to claim 2, wherein thejacket further includes a seventh opening.
 4. The sensor guide wireaccording to claim 2, wherein the first set of openings is located at adistal portion of the jacket, and the second set of openings is locatedat a proximal portion of the jacket.
 5. The sensor guide wire accordingto claim 1, wherein the jacket wall extends essentially parallel to alongitudinal axis of the sensor guide wire.
 6. The sensor guide wireaccording to claim 1, wherein the first set of openings includes exactlythree openings that are aligned in the circumferential direction of thejacket: the first opening, the second opening, and the third opening. 7.The sensor guide wire according to claim 1, wherein the pressuresensitive device is a membrane.
 8. The sensor guide wire according toclaim 7, wherein the sensor element further comprises one or morepiezoresistive elements provided on the membrane.
 9. The sensor guidewire according to claim 1, wherein the first set of openings is locatedat a distal portion of the jacket.